Halo Shape and Relic Density Exclusions of Sommerfeld-Enhanced Dark Matter Explanations of Cosmic Ray Excesses

TL;DR

This paper demonstrates that dark matter models with Sommerfeld enhancement cannot simultaneously explain cosmic ray excesses and match observed relic densities and halo shapes, challenging their viability.

Contribution

It provides new constraints on Sommerfeld-enhanced dark matter explanations for cosmic ray excesses based on relic density and galactic halo observations.

Findings

Thermal relic densities are too small for the required enhancement.

Elliptical galactic halos exclude large Sommerfeld enhancement.

Resonant enhancement does not alter these constraints.

Abstract

Dark matter with Sommerfeld-enhanced annihilation has been proposed to explain observed cosmic ray positron excesses in the 10 GeV to TeV energy range. We show that the required enhancement implies thermal relic densities that are too small to be all of dark matter. We also show that the dark matter is sufficiently self-interacting that observations of elliptical galactic dark matter halos exclude large Sommerfeld enhancement for light force carriers. Resonant Sommerfeld enhancement does not modify these conclusions, and the astrophysical boosts required to resolve these discrepancies are disfavored, especially when significant self-interactions suppress halo substructure.